In computing, a firewall is a software or hardware-based network security system that controls the incoming and outgoing network traffic by analyzing the data packets and determining whether they should be allowed through or not, based on a rule set. A networks firewall builds a bridge between the internal network or computer it protects, upon securing that the other network is secure and trusted, usually an external network, such as the Internet, that is not assumed to be secure and trusted.
Many personal computer operating systems include software-based firewalls to protect against threats from the public Internet. Many routers that pass data between networks contain firewall components and, conversely, many firewalls can perform basic routing functions.
